Does epic mean "impressive" or just "big"?

When epic began to be used as an adjective in English it was in specific reference to the characteristics of the type of poem that bears the same name. A couple of centuries passed, and the word’s meaning came to describe other kinds of works, aside from poetry, which had similarly grand characteristics. More recently, epic has been found used in a highly colloquial fashion, in a manner that is largely synonymous with outstanding, fabulous, or impressive. Before you pass judgment on whether this new sense of epic is acceptable to you or not, you might want to consider that all the words that this sense is synonymous with have also changed their meanings dramatically: outstanding originally described something that projected or stuck out, fabulous had to do with fables, and impressive used to mean “capable of being impressed.”